Carburetor



June 16, 1931.

G. M. BICKNELL ET AL CARBURETOR Filed Feb. 25, 1929 III!!! ATTORN EY Patented June 16, 1931 UNITED STATES,

PATENT OFFICE GEORGE M. IBIGKNELL AND ARTHUR A. HAYDEN, OF ST. LOUIS, MISSOURI, ASSIGN O R S TO CARTER CARBURETOBCORPORATION, OF ST. LOUIS, MISSOURI, A CORPORATION or DrmAwAnE CARBIURETOR Application filed February 23, 1929. Serial No. 342,080.

This inven" ion relates to carburetors for internal combustion engines and particular- 1;; to the construction and arrangement of t e parts forming the air passages and the control valves therefor, with a view to procuring the highest efliciency in the operation of the carburetor, and the greatest facility in manufacture and assembly.

It is an object of the invention to produce a carburetor which is inherently convenient sible for inspection or repair. Other objects of the invention will appear from the follow ing specification and the' accompanying drawing, referring to which:

- Figure 1 shows a sectional elevation of a carburetor constructed according to our invention.

The reference numeral 1 indicates a casting forming the main body member of the carburetor. This casting'forms the walls of an air chamber 2 to which'air is admitted through an air horn 3; an annular opening 4 in the upper part of the casting is arranged to receive a flanged member 5 having an extension 6 snugly fitting into the opening; the member 5 is provided with a suitable flange 7 which, with the screws 8, serves as means to attach the flange member to the main body member.

A second flange 9 of conventional forma tion is provided for attaching the carburetor to the intake manifold of an internal combustion engine. The flanged member has a pas sageway therethrough comprising a cylindrical portion 10, a gradually downwardly and inwardly tapering portion 11, and a rather sharply outwardly flared portion 12 which extends'to and terminates in the peripheral extension or skirt 6. r

The main bod member has an annular surface 13 provi ed with a gasket to receive the upper edge of a fuel bowl 14. The body member also has a downwardly extending portion 15 to which the bowl is attached by a screw 16, as shown. The fuel is supplied to the bowl by conventional means (not shown) and maintained at a constant level therein by the usual float 17. The upper part of the extension 15 is provided with a recess 18 from which a passageway 19 extends downwardly to the end of the extension where it is closed by the screw 16. This passageway communicates with the fuel bowl through an opening 20. The main conduit 21 is screwed by means of suitable threads into the passage way 19 and extends upwardly into the recess 18. A stand pipe 22 having a suitable flange and screw threads 23 is threaded into the lower part of the recess 18 and the lower part of. the stand pipe surrounds theupper part of the main jet 21.

.A small port 24 permits communication from the chamber 2 through the recess 18 to i the accelerating well 19. The upper part of the jet 21 is loosely surrounded by an annular member 25 which is tightly fitted into the 'flange 23 of the stand pipe,=the restricted space between the bore of the member 25 and the wall of the jet'21 serving as a communication between the passageway 19 and the stand pipe 22.

A port 26 formed in the wall of thestand pipe permits restricted communication between the recess 18 and the interior of the pipe. Just above this port and approximately at the level of the upper part of the jet 21, a restrictedpassage 27 is formed in-the stand pipe to give a Venturi efi'ect.

serve to bleed air from the accelerating well 19 into the jet under certain operating conditions. Y

The stand pipe terminates at or near the restricted portion of the main Venturi, as in-' Small ports 28 are formed in the wall of the jet 21 and of substantially frustro-conical shape which is slidably mounted on the stand pipe 22.-

A manually operable shaft 33 is rotatably mounted in the walls of the casting 1 and has fixed thereto an arm 34 having a yoke to engage an annular recess in the lower part of the choke cone 32. In order to give the cone a more positive closure, it is provided with a skirt 36 near its lower end of larger diameter than the restricted portion of the venturi 28. In order to produce the most efficient design, this choke cone necessarily has a larger diameter than the distance from the bottom of the skirt 6 to the bottom of the adjacent part of the inlet passageway leading into the air chamber 2. It is accordingly necessary to provide some other and larger opening through which the choke cone may: be inserted and assembled on the stand pipe 22, for even if the choke cone itself could be inserted through the air inlet, it could not be assembledon the stand pipe. Accordingly, we make the flange member separate from the main casting 1 and provide it with screws 8 by means of which it is readily attachable and detachable. The opening 4 is of ample size to receive the choke cone and stand pipe, and they may be readily assembled in position before the flange member 5 is attached.

In order to secure anaccurate closure of the choke cone 32 on the restricted portion of the venturi, weform the threads 37 upon which the stand pipe is secured concentric with the opening 4 so that they can both be machined .at a single operation, thus assuring their absolute concentricity. The threads on the stand pipe also being conveniently made accurately concentric with the cylindrical surface of the pipe, the concentricity of the choke cone with the opening 4 is assured. In order to insure the concentricity of the venturi with the opening 4, the cylindrical surface of the skirt 6 and the flaredportion 12 of the venturi are machined from an integral piece at a sin gle operation.

Adjacent to the throttle 29, we provide a bleed opening 38 to admit air and gasoline at idling speeds. The air enters through a port 39 in the screw 40 which cooperates with the boss 41 to adjust the amount of air ad .mitted. 'A small bore 42 is drilled in'the flanged member 5'and is fitted with a small and comparatively fragile tube 43, this tube being made as small as possible and located at the side of the air chamber opposite the air inlet 3 to restrict the flow of air as little as possible. The tube is rolled down at 44 to form a highlyrestricted portion which serves to calibrate the amount of fuel passing through the tube. A- small air bleed 45 below the restriction is provided. The tube extends and also to avoid serious interference with the air flow, must be carefully protected from such strain as would result from misalignment of the bores 42 and 46. Accordingly, the holes for the screws 8 are very carefully drilled and the dowel pins 48 may also be provided, if desired, to positively retain the flanged member 5 in such a position relative to the body member 1 that these bores are in exact registration.

One important feature of this invention is that the skirt 6 extends to a point below the top of the inlet passageway 3. The fact that the skirt extends slightly downwardly into the flow of air causes a portion of the air to circulate around the outside of the skirt 6 and enter from the sides and back of the air chamber so that the air enters the flared portion 12 of the venturi evenly from all sides, and as it flows upwardly toward the restricted portion 28, a smooth and even'acceleration of the air stream occurs with a minimum amount of turbulence. By this arrangement, a much the venturi by a given suction.

Another important reason for forming the casting 5 separate from the main body member is that the outward flare 12 of the venturi gives a slanting surface against which the drill point must work when drilling the bore 42. It will be noted that the formation of the flanged member 5 separate from the body member obviates the necessity of first passing the drill through the bore 46 and then extend- ,ing it through the comparatively long space to operate against the sloping wall of the venturi. With the flange and body members formed in two separate pieces, these holes may be drilled separately in jigs so that the points of the drills may be firmly supported, and the screws 8 and dowel pins 48 may be relied upon for accurate registration of the holes. k

The operation of the device is as follows:

The carburetor being attached by means of the flange 9 to the intake manifold of an internal c'ombustion' engine, suction in the manifold draws air through the inlet 3, the venturi, the mixing chamber 31, and the valve 29 into the engine. The air stream enters the inlet at a comparatively slow rate,,and the passages are so formed that its speed is gradually increased as it passes toward the venturi 28. As it strikes the depending edge of the skirt 12, a portion of the air current is caused to flow around the 'skirt toward the back of the air chamber 2 ,and to enter the flared portion 12 0f the venturi from the sides and rear. The tube 43, being made as small as possible and located at the rear of the air chamber, presents a minimum resistance to the flow of air into the venturi.

The air stream reaches its highest velocity at the throat28 of the venturi, resulting in a considerable suction on the mouth of the stand pipe 22. This suction draws in air through the port 26 to the lower end of the stand pipe below the primary venturi 27, producing a suction at the mouth of main jet 21 and drawing fuel up through the jet from the fuel chamber. A small amountof air is also drawn in through the port 24 and the ports 28 to break up the surface tension of the fuel which is passing upwardly through the main jet. At periods of very low suction in the operation of the motor, an excess quantity of fuel flows into the accelerating well 19. Upon acceleration of the engine, this fuel is rapidly withdrawn from thewell to temporarily enrich the mixture.

In starting, or when the motor is cold, the shaft 33 is operated to slide the choke cone 32 up into the annular space between the venturi 28 and the mouth of the stand pipe 22. This restricts or entirely cuts oif the flow of air through the main venturi 28 and causes all the air to be drawn in through the ports 24 and 26.

The suction ofthe motor is transmittedv more directly to the main jet 21 and draws much larger quantities of fuel therethrough to produce an exceptionally rich mixture when the motor is cold.

When the throttle valve is closed, the suction in the primary'venturi27 and the main venturi 28 is insuflicient to draw proper quantities of fuel up through the main jet. Un-

der these conditions,,the suction of the intake manifold is transmitted to the port 38 where it draws ina small quantity of air from the mixing chamber 31 and also draws fuel and airfrom the fuel chamber through the bore 47 and the tube 43. The small opening 45 serves to bleed the air into the tube 43 and the restriction 44 serves as a metering orifice.

It will be seen that we have provided a simple, eflective, and easil manufactured device for the purpose descri ed.

We claim: 7 a

1. In a carburetor, a body member having an air chamber therein, a stand pipe mounted in a wall thereof, said chamber having a circular opening in an opposite wall of said chamber, a member having an integral annular skirt extending into said opening, and projecting into the air chamber and a passageway terminating in said skirt, said member 2. In a carburetor, a ody member forming an air chamber, an air inlet at one side of said chamber, a circular opening in the upper part of said chamber above said air inlet, a second body'member mounted in said openingand having an annular skirt depending therein to a point below the top wall of said chamber, said second member forming a mixture outlet passageway for said carburetor and have ing a valve controlling said passageway, a stand pipe comprising a primary mixing chamber mounted in a wall of said first-named body member and extending into said annular skirt, the mouth of said stand pipe being concentric with said skirt, means to admit air and fuel to the lower part of said primary mixing chamber, and means for closing the space between the mouth of said stand pipe and said skirt.

tending into said chamber to a point below' the top Wall thereof and being formed as a venturi for said passageway, a valve in said flanged member controlling said passageway, a stand pipe mounted in said body member and concentric with said circular opening, said stand pipe terminating near the restricted portion of said venturi, a choke cone s'lidably mounted on said stand pipe having a skirt port-ion of larger diameter than the restricted portion of said venturi, and means for sliding said cone along said stand pipe to close the passageway between the outer part of said pipe and said venturi.

4. In a carburetor, a main body member I having a chamber therein, an inlet opening at one side of said chamber, an annular opening in the upper part of said chamber, a primary mixing conduit mounted in a recess in a wall of said chamber, a choke member slidably.

mounted on said conduit, said conduit and said choke being insertable in said chamber only through the opening in the upperpart of said chamber, a flanged member having an 1 integral downwardly extending annular skirt extending through said upper opening and terminating at a point substantially below the top wall of said chamber, a passageway through said flanged member having a re stricted portion substantially at the level of the upper part of the mixing conduit, a throttle valve mounted in said flanged member and controlling the passageway therethrough, said choke member being of larger diameter than the restricted portion of said passageway, and means for securing the flanged mem- V ber to the main body member.

5. In a carburetor, a body member having -an air chamber therein, an inlet opening for said chamber of comparatively large size, a

downwardly extending projection on said body member, means forming a fuel chamber encircling said projection, said projection extending within said chamber andserving as a ba-file to direct the flow of air, a recess in the upper portion of said extension, said recess forming a downwardly extending portion of said chamber, a vertical conduit threaded into said recess and extending upwardly into said chamber, said conduit forming a primary mixing chamber, a substantially frustro-comcal annular member slidably mounted on said conduit, a separate and distinct body member mounted on said first-named body member, an opening in said chamber, a passageway in said second-named body member registering with said opening, said assageway having a restricted portion atsu stantially the level of the upper part of said conduit, a throttle valve in said second named body member to control the passageway therethrough and manually operable means for moving said frustro-conical member into or out of said restricted portion.

6. In a carburetor, a body member having an air chamber therein, an inlet opening for said air chamber, a circular opening substantially at right angles to said inlet opening, an integral casting having an annular skirt extending into said second-named opening and forming a battle within said chamber for directing the flow of air, a passageway through said casting forming an outlet passageway for the carburetor, said passageway having a restricted portion within said annular skirt, a

, stand pipe mounted in said chamber and extending substantially to the restricted portion of said assageway, an'annular member of substantlally frustro-conical shape slidably mounted on said conduit and movable toward or away from said restricted portion, the larger portion of said frustro-comcal member being larger than the restricted portion of said passageway.

7; In a carburetor, a body member forming an air chamber, an inlet for said chamber, an outlet opening for said chamber, a flanged Venturi member fitted to said outlet opening and having an integral annular bafiie extending therein'to a point substantially beyond the wall of the chamber, a choke member in said chamber movable toward said annular baffle to control the flow through said outlet, said choke member being insertable only by the removalof said battle, and means for releasably attaching said flanged member to said body member.

In testimony whereof, we aflix our signatures this 13th day of February, 1929.

GEORGE M. BIOKNELL. ARTHUR A. HAYDEN. 

